The ability to covertly process information is important in the operations of military, law enforcement, surveillance, and hunting. Normal information processing utilizing visible light cannot be used during covert conditions, especially in darkness, as the visible light can compromise the sender's position. Such usage is also problematic for situations in which stealth conditions must be maintained in the dark but at the same time information from the display must be visible.
Electronic information displays present a particular problem. The use of these devices has become ubiquitous for displaying information of all kinds. For example, soldiers in the field constantly rely on information displays such as laptop computers, tablets, cell phones, GPS devices to obtain information critical to their operation. At night time and in the dark, these screens are readily visible over long distances due to the emission of visible light which can compromise covert operations. With the advent of bright LED backlit displays, the visible light can easily be seen over long distances and hence the danger of compromising cover operations has become greater.
Maintaining stealth conditions when using information displays is also difficult and time consuming and can easily be compromised. For example, when the use of a display is required, a light-blocking hood must first be deployed over the display before it is turned on. The hood is to block all visible light emanating from the display. Then the observer must put their head under the hood and turn on the display to read it. After obtaining the required information, the display must be turned off and then the hood removed. An additional complication is that night vision goggles are routinely worn in dark conditions to improve vision. Night vision goggles work by detecting and amplifying infrared light to which the human eye is not sensitive. The goggles must be removed before viewing a display screen because the brightness of the display will damage the goggles and render them unusable. Goggle removal is cumbersome and adds additional time to the process of reading the information. This process for viewing a display screen in the dark under stealth conditions increases the amount of time it takes to obtain the information, adding inefficiencies to the operation. There is also a high likelihood that inadvertent leakage of light will occur, compromising the covert operation. There is, therefore, a need to process information emanating from a display which emits in the infrared, but not in the visible, in the dark under stealth conditions and that can be read using an infrared detector such as night vision goggles. There is also a need to be able to easily use a standard display device both in the standard visible mode and infrared mode.
Covert observation of one's surroundings is another aspect of covert information processing. For example, in order to navigate a road in the dark, the road must be illuminated and the information of the observed images processed. For covert operations, visible light cannot be used so there is a need for efficient infrared illumination and the information read using an infrared detector. In the same way that covert observation of one's surroundings can be made possible by providing sufficient infrared illumination for interrogation with infrared detectors, visible information used for identification or authentication can be hidden such that only an infrared signal can be detected. It would be advantageous if standard visible light sources including headlights, flashlights, and light stick illuminators could be quickly and easily converted to efficient infrared illuminators when needed and then back again.